Association of serum 25-hydroxyvitamin D3 and D2 with academic performance in childhood: findings from a prospective birth cohort

1MRC Centre for Causal Analyses in Translational Epidemiology, School of Social and Community Medicine, University of Bristol,
Bristol, UK

2School of Social and Community Medicine, University of Bristol, Bristol, UK

3Norwich Medical School, University of East Anglia, Norwich, UK

Correspondence to Dr Anna-Maija Tolppanen, MRC Centre for Causal Analysis in Translational Epidemiology, School of Social and Community Medicine,
University of Bristol, Oakfield House, 15-23 Oakfield Grove, Clifton, Bristol BS8 2BN, UK; anna-maija.tolppanen{at}uef.fi Professor Debbie A Lawlor, MRC Centre for Causal Analysis in Translational Epidemiology, School of Social and Community Medicine,
University of Bristol, Oakfield House, 15-23 Oakfield Grove, Clifton, Bristol BS8 2BN, UK; d.a.lawlor{at}bristol.ac.uk

Contributors Planned the research project: A-MT and DAL. Obtained funding: DAL. Provided essential materials: WDF (laboratory analyses).
Data analysis: A-MT and AS. Supervised the analyses and project: DAL. Wrote the first draft of the manuscript: A-MT and DAL.
Accepted the final manuscript and made important intellectual contribution to draft versions: A-MT, AS, WDF and DAL. Acts
as guarantor: A-MT.

Accepted 13 February 2012

Published Online First 9 April 2012

Abstract

Background Higher total serum 25-hydroxyvitamin D (25(OH)D) concentrations have been associated with better cognitive function mainly
in cross-sectional studies in adults. It is unknown if the associations of different forms of 25(OH)D (25(OH)D3 and 25(OH)D2) are similar.

Methods Prospective cohort study (n=3171) with serum 25(OH)D3 and 25(OH)D2 concentrations measured at mean age of 9.8 years and academic performance at age 13–14 years (total scores in English, mathematics
and science) and 15–16 years (performance in General Certificates of Education examinations).

Results Serum 25(OH)D3 concentrations were not associated with any educational outcomes. Higher 25(OH)D2 concentrations were associated with worse performance in English at age 13–14 years (adjusted SD change per doubling in 25(OH)D2 (95% CI) −0.05 (−0.08 to −0.01)) and with worse academic performance at age 15–16 years (adjusted OR for obtaining ≥5 A*–C
grades (95% CI) 0.91 (0.82 to 1.00)).

Conclusion The null findings with 25(OH)D3 are in line with two previous cross-sectional studies in children. It is possible that the positive association of 25(OH)D
with cognitive function seen in adults does not emerge until later in life or that the results from previous cross-sectional
adult studies are due to reverse causality. The unexpected inverse association of 25(OH)D2 with academic performance requires replication in further studies. Taken together, our findings do not support suggestions
that children should have controlled exposure to sunlight, or vitamin D supplements, in order to increase academic performance.

Footnotes

Funding Work on this study is funded by an UK Medical Research Council (MRC) Grant G0701603, which also pays A-MT's salary. Salary
support for AS is provided by Wellcome Trust grant ref 079960. MRC, the Wellcome Trust and the University of Bristol provide
core funding support for ALSPAC. The MRC and the University of Bristol provide core funding for the MRC Centre of Causal Analyses
in Translational Epidemiology (Grant G0600705). The views expressed in this paper are those of the authors and not necessarily
those of any funding body or others whose support is acknowledged. The funders had no role in study design, data collection
and analysis, decision to publish or preparation of the manuscript.

Competing interests None.

Ethics approval ALSPAC Law and Ethics Research Committee and local research ethics committee.